1. Field of the Invention
The present invention relates to an image measuring system, image measuring method and image measuring program provided with a nonstop measurement mode for moving an imaging means relative to a measurement stage that supports an object to be measured and taking in instantaneous image information without making a stop at a designated measurement location.
2. Description of the Related Art
A conventional CNC image measuring machine moves a measurement stage relative to an imaging means such as a CCD camera, as shown in FIG. 13, and makes a stop at a measurement location. Then, it adjusts the amount of illuminative light to acquire image information about an object to be measured, and applies image processing such as measuring tool setting and edge detection to the acquired image information, thereby executing a measurement at one measurement location. This measurement is repeatedly executed as Measurement 1, Measurement 2, . . . at all measurement locations to complete measurements at required locations (hereinafter such the measurement mode is referred to as a “standard mode”).
In contrast, for the purpose of improving the measurement throughput, an image measuring machine is proposed, which has a measurement mode for measuring without making no stop of the measurement stage relative to the imaging means even at the measurement location (hereinafter such the measurement mode is referred to as a “nonstop measurement mode”) (JP 2004-535587A, paragraphs 0005-0006, FIG. 2). This image measuring machine irradiates the object with strobe illumination or uses a shuttered CCD camera to capture instantaneous image information without making no stop of the measurement stage at measurement locations as shown in FIG. 14. Then, it takes in the captured instantaneous image information for image measuring. This image measuring machine positions the CCD camera fast and roughly in the measurement region and, after deceleration, it takes in an image in a slow region.
The above-described conventional image measuring machine has no problem if the measurement locations are arranged along a straight line. To the contrary, if they are not arranged along a straight line, when the speed of the measuring machine is kept constant to execute measurements at measurement locations, a problem may arise. Namely, a larger variation angle of the advancing direction, with a measurement pulse such as a square (a directional variation angle of 90°) or a Z-shape (a directional variation angle of 90° or more), requires an addition of a larger acceleration to follow a turning location (hereinafter referred to as a bent point) and accordingly overloads the machine. This results in vibrations of the machine and causes shakes of subsequent captured images (deterioration of the image quality) and shakes of imaging positions, which deteriorate measurement accuracy of the image. In some cases, the overload may blow a protective fuse.
The present invention has been made in consideration of such the problem and has an object to provide an image measuring system, image measuring method and image measuring program capable of preventing deterioration of measurement accuracy and of imposing no overload on any movement mechanism.